Refrigerant compositions and use thereof in low temperature refrigeration systems

ABSTRACT

A process for obtaining low temperature refrigeration in an existing or new low temperature refrigeration system designed to operate with, or suitable for use with, or capable of being used with HCFC-22 as the refrigerant, the refrigerant composition being a refrigerant composition comprising difluoromethane (HFC-32), pentafluoroethane (HFC-125) and tetrafluoroethane (HFC134a), the three components being present in the composition in amounts such that the operating characteristic of the refrigerant composition in regard to superheat is provided at an acceptable level and the operating characteristics of the refrigerant composition in regard to cooling capacity, mass flow and efficiency (COP) characteristics, when employed as the refrigerant in a low temperature refrigeration system, are each at least 95% of the operating characteristics of chlorodifluoromethane (HCFC-22) if HCFC-22 were to be employed as the refrigerant in such low temperature refrigeration system.

RELATED APPLICATION

This application claims priority from U.S. Provisional Application No.60/488,042, filed Jul. 17, 2003.

FIELD OF THE INVENTION

This invention relates to refrigerant compositions for replacement ofozone-depleting refrigerant HCFC-22 for heating and coolingapplications, especially in low temperature refrigerant systems, and toa process for retrofitting a low temperature refrigerant systemcontaining HCFC-22 refrigerant with a refrigerant composition withoutthe necessity for any significant modification of the refrigerantsystems components or lubricants, yet still being able to obtain atleast about 95% of the operating characteristics of the R-22 compositionin such refrigerant systems. The invention also relates to a process forusing such R-22 replacement refrigerant compositions in other systemscapable of using R-22 refrigerant compositions such as newly designedsystems.

BACKGROUND TO THE INVENTION

Mechanical refrigeration systems, and related heat transfer devices suchas heat pumps and air conditioners, using refrigerant liquids are wellknown in the art for industrial, commercial and domestic uses.Chlorofluorocarbons (CFCs) were developed in the 1930s as refrigerantsfor such systems. However, since the 1980s the effect of CFCs on thestratospheric ozone layer has become the focus of much attention. In1987 a number of governments signed the Montreal Protocol to protect theglobal environment setting forth a timetable for phasing out the CFCproducts. CFC's were replaced with more environmentally acceptablematerials that contain hydrogen or hydrochlorofluorocarbons (HCFC's).Subsequent amendments to the Montreal protocol accelerated the phase-outof these CFCs and also scheduled the phase-out of HCFCs. Thus, there isa requirement for a non-flammable, non-toxic alternative to replacethese CFCs and HCFCs. In response to such demand industry has developeda number of hydrofluorocarbons (HFCs), which have a zero ozone depletionpotential.

The importance of refrigeration systems, especially low temperaturerefrigeration systems, to the food manufacture, distribution and retailindustries is fundamental. Such systems play a vital role in ensuringthat food which reaches the consumer is both fresh and fit to eat. Insuch low temperature refrigeration systems the popular refrigerantemployed has been chlorodifluoromethane (R-22 or HCFC-22), which has anozone-depleting potential and will be phased out completely.

A number of patent publications have suggested replacements for HCFC-22.That is, these patent publications have suggested refrigerants orrefrigerant compositions that can be used instead of HCFC-22 in newrefrigeration systems to be built or installed. Among such patentpublications there may be mentioned U.S. Pat. No. 5,185,094, U.S. Pat.No. 5,370,811, U.S. Pat. No. 5,438,849, U.S. Pat. No. 5,643,492, U.S.Pat. No. 5,709,092, U.S. Pat. No. 5,722,256, U.S. Pat. No. 6,018,952,U.S. Pat. No. 6,187,219 B1, U.S. Pat. No. 6,606,868 B1, U.S. Pat. No.6,669,862 B1, published US application no. US 2004/00691091 A1, andpublished European application nos. EP 0 430169 A1, EP 0 509 673 A1 andEP 0 811 670 A1. While all the mentioned US patents and published EPapplications disclose ternary mixtures of difluoromethane (HFC-32),pentafluoroethane (HFC-125) and tetrafluoroethane (HFC134a) for use inrefrigeration or air conditioning systems, they do not address theability to replace HCFC-22 in existing R-22 refrigeration systems orsystems suitable for use with R-22 refrigerant, particularly in lowtemperature refrigeration systems, while obtaining at least about 95% ofthe operating characteristics of R-22 without the necessity formodification of the system, especially without the necessity foradjustment or replacement of the expansion valve of the low temperaturerefrigeration system. Comparative examples provided later in the presentspecification of this application show that tertiary compositions withinthe scope of the prior art disclosure are not suitable for use in lowtemperature R-22 refrigeration systems. Those prior art compositions donot obtain at least about 95% of the operating characteristics of R-22so as to enable one to use such compositions in low temperature R-22refrigeration systems over a wide range of low refrigerationtemperatures and ambient temperatures without the necessity formodification of the system.

In order to retrofit an existing low temperature refrigeration systememploying HCFC-22 refrigerant with replacement refrigerant, it isnecessary that that the replacement refrigerant operatingcharacteristics, such as evaporator superheat, cooling capacity,refrigerant mass flow rate, efficiency, pressure and energy consumption,are substantially identical to that of the HCFC-22 refrigerant beingreplaced. This near match in properties of the replacement refrigerantto those of HCFC-22 are essential for their use in such existing lowtemperature refrigeration systems or systems designed for using R-22refrigerant, without requiring equipment replacement or modification,e.g. replacement or modification of expansion valves of the lowtemperature refrigeration system. The solutions suggested by theindustry for R-22 replacements, such as R-407A and R-407C refrigerants,do not solve this problem since they require modification of the systemsin an attempt to match R-22 operating characteristics.

SUMMARY OF THE INVENTION

It has been discovered that a ternary refrigerant compositions of about25 to about 35, preferably about 30, mass percent difluoromethane(HFC-32), about 20 to about 40, preferably about 25 to about 35, andmore preferably about 30 mass percent pentafluoroethane (HFC-125) andabout 35 to about 45, preferably about 40, mass percenttetrafluoroethane (HFC134a), and especially a composition of about 30mass percent HFC-32, about 30 mass percent HFC-125 and about 40 masspercent HFC134a are especially useful to retrofit existing lowtemperature refrigeration systems employing HCFC-22 refrigerant. Therefrigerant compositions of this invention may also be employed insystems suitable for or capable of use with R-22 refrigerant such asexisting, new or newly designed low temperature refrigeration systems.The ternary refrigerant compositions of this invention substantiallymatch the operating characteristics of HCFC-22 refrigerant, especiallyin, desired evaporator superheat, cooling capacity, mass flow andefficiency, i.e., COP (coefficient of performance that is the ratio ofrefrigeration effect to the energy required) and thereby enable theternary compositions of this invention to replace HCFC-22 in existinglow temperature refrigeration systems or in refrigeration systemssuitable for use with R-22 refrigerant, without requiring anysignificant system modification, such as adjustment, replacement orredesign of the R-22 system expansion valve. The values of the operatingcharacteristics of the ternary compositions of this invention willgenerally be at least 95% or more, and preferably at least about 98% ormore of the corresponding values of the operating characteristics ofHCFC-22 in the low temperature refrigeration systems in which theternary composition is to replace the HCFC-22 refrigerant. Also, thecompositions employed in this invention are essentially non-flammablewhen tested in accordance with ASTM E681-2001 at conditions described inASHRAE Standard 34 addendum P (3^(rd) public review, January 1998).

In one aspect, the invention relates to a refrigerant compositioncomprising difluoromethane (HFC-32), pentafluoroethane (HFC-125) andtetrafluoroethane (HFC134a), the three components being present in thecomposition in amounts such that the operating characteristics of therefrigerant composition in regard to superheat provided duringrefrigeration is provided at a n acceptable superheat level, and theoperating characteristics of cooling capacity, mass flow characteristicsand efficiency (COP), when employed as the refrigerant in a lowtemperature refrigeration system are each at least 95% and preferably98% of the operating characteristics of chlorodifluoromethane (HCFC-22)if HCFC-22 were to be employed as the refrigerant in such lowtemperature refrigeration system.

In another aspect, this invention relates to a process for producing lowtemperature refrigeration in a low temperature refrigeration systemsuitable for use with HCFC-22 refrigerant, which system achieves andmaintains an evaporator temperature of below 32° F. (0° C.), or about14° F. (−10° C.) or below, or about 5° F. (−15° C.) or below, and evenabout −22° F. (−30° C.) or below, the process comprising condensing arefrigerant and thereafter evaporating the refrigerant with anevaporator in the vicinity of a body to be cooled, wherein therefrigerant composition comprises from about 25 to about 35 mass %difluoromethane (HFC-32), from about 20 to about 40 mass %pentafluoroethane (HFC-125), and from about 35 to about 45 mass %tetrafluoroethane (HFC-134a) whereby these three components are presentin the refrigerant composition such that the operating characteristic ofevaporator superheat provided during refrigeration is in the range offrom about 80 to about 16° F. (about 4.4 to about 8.9° C.) for anevaporation temperature range of about 15 to 30° F. (about −9 to −1°C.), in the range of from about 80 to about 12° F. (about 4.4° to about6.7° C.) for an evaporation temperature of about −15° F. (about −26°C.), or in the range of from about 40 to about 8° F. (about 2.2° toabout 4.4° C.) for an evaporation temperature of about −30° F. (about−34° C.), and the operating characteristics of the refrigerantcomposition in regard to cooling capacity, efficiency (COP), and massflow, when employed as the refrigerant in the refrigeration system, areeach at least about 95% of those operating characteristics ifchlorodifluoromethane (HCFC-22) were to be employed as the refrigerantin said refrigeration system at identical refrigeration conditions.Another feature of the invention is such low temperature refrigerationsystems comprising an evaporator and condenser and containing therefrigerant composition of this invention.

In a further aspect, this invention relates to a process for producinglow temperature refrigeration in a low temperature refrigeration systemthat achieves and maintains an evaporator temperature of below 32° F.(0° C.) or about 14° F. (−10° C.) or below, or about 5° F. (−15° C.) orbelow, and even about −22° F. (−30° C.) or below and haschlorodifluoromethane (HCFC-22) as a refrigerant therein, the processcomprising replacing, and preferably essentially totally replacing, thechlorodifluoromethane (HCFC-22) refrigerant in the refrigeration systemwith a replacement refrigerant composition comprising the threecomponents: difluoromethane (HFC-32), pentafluoroethane (HFC-125), andtetrafluoroethane (HFC-134a), condensing the replacement refrigerantcomposition and thereafter evaporating the replacement refrigerantcomposition with an evaporator in the vicinity of a body to be cooled,wherein the refrigerant composition comprises from about 25 to about 35mass % difluoromethane (HFC-32), from about 20 to about 40 mass %pentafluoroethane (HFC-125), and from about 35 to about 45 mass %tetrafluoroethane (HFC-134a) whereby these three components are presentin the refrigerant composition such that the operating characteristic ofsuperheat provided during refrigeration is in the range of from about 80to about 16° F. (about 4.4 to about 8.9° C.) for an evaporationtemperature range of about 15 to 30° F. (about −9 to −1° C.), in therange of from about 80 to about 12° F. (about 4.4° to about 6.7° C.) foran evaporation temperature of about −15° F. (about −26° C.), or in therange of from about 4° to about 8° F. (about 2.2° to about 4.4° C.) foran evaporation temperature of about −30° F. (about −34° C.), and theoperating characteristics of the refrigerant composition in regard tocooling capacity, efficiency (COP), and mass flow, when employed as therefrigerant in the refrigeration system, are each at least about 95% ofthose operating characteristics if chlorodifluoromethane (HCFC-22) wereto be employed as the refrigerant in said refrigeration system atidentical refrigeration conditions. “Essentially totally replacing”means that some slight amount, generally less than about 5%, preferablyless than about 3%, and more preferably less than about 1%, of HCFC mayinadvertently remain in the system upon the replacement.

A still further aspect of this invention is in providing a process forproducing low temperature refrigeration in a new low temperaturerefrigeration system suitable to be used with chlorodifluoromethane(HCFC-22) that achieves and maintains a temperature of below 32° F. (0°C.) or about 14° F. (−10° C.) or below, or about 5° F. (−15° C.) orbelow, and even about −22° F. (−30° C.) or below and designed to beoperated with chlorodifluoromethane (HCFC-22) as a refrigerant therein,the process comprising condensing a refrigerant composition andthereafter evaporating the refrigerant composition with an evaporator inthe vicinity of a body to be cooled, wherein the refrigerant compositioncomprises from about 25 to about 35 mass % difluoromethane (HFC-32),from about 20 to a bout 40 mas % pentafluoroethane (HFC-125), and fromabout 35 to about 45 mass % tetrafluoroethane (HFC-134a) whereby thesethree components are present in the refrigerant composition such thatthe operating characteristic of superheat provided during refrigerationis in the range of from about 80 to about 16° F. (about 4.4 to about8.9° C.) for an evaporation temperature range of about 15 to 30° F.(about −9° to −1° C.), in the range of from about 8° to about 12° F.(about 4.4° to about 6.7° C.) for an evaporation a temperature of about−15° F. (about −26° C.), or in the range of from about 4° to about 8° F.(about 2.2° to about 4.4° C.) for an evaporation temperature of about−30° F. (about −34° C.), and the operating characteristics of therefrigerant composition in regard to cooling capacity, efficiency (COP),and mass flow, when employed as the refrigerant in the refrigerationsystem, are each at least about 95% of those operating characteristicsif chlorodifluoromethane (HCFC-22) were to be employed as therefrigerant in said refrigeration system at identical refrigerationconditions. The phrase “suitable to be used with chlorodifluoromethane(HCFC-22)” means a system has used, or can, or is capable of usingchlorodifluoromethane (HCFC-22) refrigerant in the system to obtain thelow temperature refrigeration.

A yet another aspect of this invention is to provide the refrigerationprocesses described wherein there is no necessity for adjustment(including redesign) or replacement of any chlorodifluoromethane(HCFC-22) system expansion valve of the low temperature refrigerationsystem in order to obtain the stated operating characteristic. Stillfurther aspects of the invention relate to such refrigeration processeswherein the low temperature refrigeration achieves and maintains atemperature of about 14° F. (−10° C.) or below, or of about 5° F. (−15°C.) or below, and also a temperature of about −22° F. (−30° C.) orbelow.

Although the refrigerant compositions of this invention have beenformulated to be useful to replace HCFC-22 refrigerant in existing lowtemperature refrigeration systems and other low temperaturerefrigeration systems suitable for using chlorodifluoromethane (HCFC-22)refrigerant, it will be appreciated that use of such refrigerantcompositions of this invention is not limited to such use but will haveother refrigerant uses, such as, for example, in non-low temperaturerefrigeration systems.

BRIEF DESCRIPTION OF THE DRAWING

In the drawings FIG. 1 is a graph of the refrigerant compositions ofthis invention outlining the proportions of the tertiary compositioncomponents, and showing their close proportional relationship to twocomparative refrigerant compositions examples outside the scope of theinvention that were tested in a low temperature refrigeration system andshown not to provide at least about 95% of the operating characteristicsof R-22 over a wide range of low temperature operating temperatureswithout the necessity for modification of the system.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that specific ternary refrigerant compositionscan be utilized in a process for producing low temperature refrigerationin a low temperature refrigeration system suitable for use with HCFC-22refrigerant, which system achieves and maintains an evaporatortemperature of below 32° F. (0° C.), or about 14° F. (−10° C.) or below,or about 5° F. (−15° C.) or below, and even about −22° F. (−30° C.) orbelow, the process comprising condensing a refrigerant and thereafterevaporating the refrigerant with an evaporator in the vicinity of a bodyto be cooled, wherein the refrigerant composition comprises from about25 to about 35 mass % difluoromethane (HFC-32), from about 20 to a bout40 mass % pentafluoroethane (HFC-125), and from about 35 to about 45mass % tetrafluoroethane (HFC-134a) whereby these three components arepresent in the refrigerant composition such that the operatingcharacteristic of superheat provided during refrigeration is in therange of from about 80 to about 16° F. (about 4.4 to about 8.9° C.) foran evaporator temperature range of about 15 to 30° F. (about −9° to −1°C.), in the range of from about 8° to about 12° F. (about 4.4° to about6.7° C.) for an evaporator temperature of about −15° F. (about −26° C.),or in the range of from about 4° to about 8° F. (about 2.2° to about4.4° C.) for an evaporator temperature of about −30° F. (about −34° C.),and the operating characteristics of the refrigerant composition inregard to cooling capacity, efficiency (COP), and mass flow, whenemployed as the refrigerant in the refrigeration system, are each atleast about 95% of those operating characteristics ifchlorodifluoromethane (HCFC-22) were employed as the refrigerant in saidrefrigeration system at identical refrigeration conditions.

The phrase “low temperature refrigeration system” means a refrigerationsystem that achieves and maintains an evaporator temperature of below32° F. (−0° C.), preferably about 14° F. (−10° C.) or below, and moreparticularly about 5° F. (−15° C.) or below, and especially atemperature of about −22° F. (−30° C.) or below.

The term “superheat” means the temperature rise of the refrigerant atthe exit of the evaporator above the saturated vapor temperature (or dewtemperature) of the refrigerant.

The term “COP” is a measure of energy efficiency and means the ratio ofrefrigeration or cooling capacity to the energy requirement of therefrigeration system, i.e., energy to run the compressor.

The term “mass flow rate” means to the amount (pounds) of refrigerantflowing through a conduit of a given size in a given amount of time.

The term “capacity” refers to the amount of cooling provided, inBTUs/hr, by the refrigerant in the refrigeration system. This isexperimentally determined by multiplying the change in enthalpy, inBtu/lb, of the refrigerant as it passes through the evaporator by themass flow rate of the refrigerant. The enthalpy can be determined from ameasurement of the pressure and temperature of the refrigerant.

Refrigerant compositions that do not meet both the evaporator superheatrequirements and have values for their operating characteristics, suchas capacity, COP and mass flow rate, in low temperature refrigerationsystems that will be at least 95% of the corresponding values of theoperating characteristics of HCFC-22 in an identical low temperaturerefrigeration system are not suitable for use in replacing HCFC-22refrigerant in such low temperature refrigeration systems since the useof such compositions will generally require modification or replacementor redesign of the HCFC-22 refrigeration system components, such asexpansion valve used in HCFC-22 refrigeration systems, and thus lead toundesired expense and downtime for the systems. In contrast, the ternaryrefrigerant compositions of this invention do have the ability tosubstantially match evaporator superheat requirements and meet at least95% or more of the value of, operating characteristics (such as, coolingcapacity, efficiency and mass flow), of HCFC-22 in low temperaturerefrigeration systems across a wide range of refrigeration conditions,e.g., evaporator and ambient temperatures,

The surprising ability of the ternary refrigerant compositions of thisinvention to substantially match operating characteristics of HCHC-22 inlow temperature refrigeration systems across a wide range ofrefrigeration conditions, e.g., evaporator and ambient temperatures, andthe inability of the compositions within the scope of the prior art andother comparative compositions to substantially match such operatingcharacteristics of HCFC-22 in such systems is illustrated by thefollowing non-limiting, examples.

Ternary compositions in accordance with this invention were prepared byproducing mixtures of the refrigerants HFC-32, HFC-125 and HFC-134a inthe amounts indicated in the following Table 1. The compositions weresubjected to thermodynamic analysis to determine their ability to matchthe operating characteristics of HCFC-22 (R-22) in a low temperaturerefrigeration system. This analysis was performed using properties fromthe National Institute of Science and Technology (NIST) Reference FluidThermodynamic and Transport Properties Database (Refprop 7.0, NIST Std.Database, 2002). The assumptions used to conduct the analysis are thefollowing. All calculations were performed assuming an averageevaporation temperature of −25° F. (−31.7° C.) and 25° F. (13.9° C.)total super heat including 10° F. (5.5° C.) useful (in evaporator).Average condensing temperature is equal to ambient temperature plus 15°F. (8.3° C.). Capacity is based on 1 cu. ft./min (0.028 m³/min)compressor displacement. COP assumes 65% isentropic compressorefficiency.

The results of the performance prediction for the compositions of thisinvention relative to HCFC-22 (R-22) are set forth in the followingTable 1.

TABLE 1 Composition Ambient Capacity Btu/hr (watts) Mass Flow lb/min(kg/min) COP components temperature % Relative to % Relative to %Relative to (mass percent) ° F. (° C.) Value HCFC-22 value Value HCFC-22value Value HCFC-22 value HCFC-22 60° (15.5°) 1771 (519) N/A 0.404(.184) N/A 2.08 N/A 80° (26.6°) 1662 (487) N/A 0.404 (.184) N/A 1.74 N/A95° (35°) 1550 (454) N/A 0.404 (.184) N/A 1.46 N/A HFC-32 (30%) 60°(15.5°) 1837 (538) 103.7% 0.419 (.190) 103.7% 1.97 94.7% HFC-125 (30%)80° (26.6°) 1662 (494) 101.4% 0.416 (.189) 103.0% 1.62 93.1% HFC-134a(40%) 95° (35°) 1529 (448)  98.6% 0.413 (.188) 102.2% 1.34 91.8% HFC-32(25%) 60° (15.5°) 1776 (520) 100.3% 0.427 (.194) 105.7% 1.96 94.2%HFC-125(35%) 80° (26.6°) 1623 (476)  97.7% 0.424 (.193) 105.0% 1.6192.5% HFC-134a (40%) 95° (35°) 1466 (430)  94.6% 0.420 (.191) 104.0%1.33 91.1%

The substantially identical match of the operating characteristics ofthe ternary refrigerant compositions of this invention to that ofHCFC-22 demonstrates that such ternary compositions can be used toretrofit existing low temperature HCFC-22 refrigerant-containingrefrigeration systems without any significant modification to therefrigeration system components. This match also demonstrates that thecompositions of this invention can be used in any low temperaturerefrigeration system suitable for use with HCFC-22.

A ternary composition in accordance with this invention, as well as twocomparative compositions in accordance with the disclosure in prior artpublication EP 0 509 673 A1, comprising mixtures of the refrigerantsHFC-32, HFC-125 and HFC-134a in the amounts indicated in the followingTable 2, were subjected to thermodynamic analysis to determine theirability to substantially match the operating characteristics of HCFC-22in a low temperature refrigeration system operating at −25° F. (−31.7°C.) evaporation temperature and 110° F. (43° C.) condensing temperature.This analysis was performed using properties from the National Instituteof Science and Technology (NIST) Reference Fluid Thermodynamic andTransport Properties Database (Refprop 7.0, NIST Std. Database, 2002).The assumptions used to conduct the analysis are the following. Allcalculations were performed assuming an average evaporation temperatureof −25° F. (−31.7° C., and 25° F. (13.9° C.) total super heat at thecompressor which includes 10° F. (5.5° C.) useful in the evaporator.Average condensing temperature is equal to ambient temperature plus 15°F. (8.3° C.). Capacity is based on 1 cu. ft./min ((0.028 m³/min)compressor displacement. COP assumes 65% isentropic compressorefficiency.

The results of the thermodynamic analysis are reported in Table 2.

TABLE 2 Capacity Btu/hr Mass Flow lb/min (watts) (kg/min) Composition %Relative % Relative components to HCFC-22 to HCFC-22 (wt percent) Valuevalue Value value HCFC-22 (100%) 1550 0.404 (454) (.184) HFC-32 (35%)1458 94.1% 0.350 86.7% HFC-125 (10%) (427) (.159) HFC-134a (55%)Comparative composition HFC-32 (30%) 1402 90.5% 0.355 88.0% HFC-125(15%) (411) (.161) HFC-134a (55%) Comparative composition HFC-32 (30%)1529 98.6% 0.413 102.2%  HFC-125 (30%) (448) (.188) HFC-134a (40%)Inventive composition

As can be seen from the data above, for the comparative compositions ofthe prior art, their operating characteristics are not substantiallyidentical to the operating characteristic of HCFC-22 in capacity andmass flow and therefore are not considered suitable to replace HCFC-22refrigerant in existing low temperature refrigeration systems withoutthe need to change other components of the refrigeration system. Incontrast thereto, the data for the compositions of this invention aresubstantially identical to the operating characteristics of the HCFC-22refrigerant and, therefore, are suitable to replace HCFC-22 refrigerantin existing low temperature refrigeration systems without the need tochange components of the refrigeration system. This match alsodemonstrates that the compositions of this invention can be used in anylow temperature refrigeration system suitable for use with HCFC-22.

The criticality of the proportions of the components of the ternarycomposition of the present invention is demonstrated by the followingcomparative testing. The comparative testing, in relationship to anHCFC-22 (R-22) composition, is comparative testing of three ternarycompositions of this invention (designated compositions LT, LT1 and LT2)with two closely related prior art ternary compositions (designatedR-407A and R-407C) having proportions of the three components outsidethe ranges of the component proportions of this invention. Thecompositions are further identified in Table 3.

Comparison in a Typical Commercial Refrigeration System The compositionswere tested with the refrigerant the system was designed for, HCFC-22,to serve as a baseline for subsequent tests. All three inventivecompositions performed nearly identical to that of the baseline HCFC-22(R-22). There was no need to adjust the expansion valve much lessreplace it. Refrigerant mass flow rate, cooling capacity, and efficiency(COP) matched that of HCFC-22 within expected measurement error. Otherrefrigerants R-407A and R-407C did not perform adequately. Using thesecomparative refrigerants would require change of system components suchas the expansion valve and possibly the evaporator.

The commercial refrigeration system equipment employed was acommercially available condensing unit and an evaporator for a walk-infreezer/cooler. The following is a detailed description of theequipment:

Condensing Unit

Unit as manufactured by Keeprite Refrigeration, Branfford, OntarioModel K350L2 outdoor, air cooled, low temperature, R-22 condensing unitequipped with:460 volts/60 Hz./3 phase electrical,2DF-0300 Copeland compressor,with demand cooling for low temperature conditions andKAKA-020 Copeland compressor for higher temperature conditionssuction accumulator, oil separator with solenoid,receiver,two valve flooded head pressure control system, andstandard operating controls.

Evaporator

Unit as manufactured by Keeprite Refrigeration.Model KUCB204DED electric defrost, low profile DX fed evaporator with:230 volts/60 Hz./1 phase electrical,electric defrost heaters,17,340 BTUH @−20 deg. F. SST, 10 degree TD,3,200 CFM air flow, andSporlan distributor and TXV.The evaporator was installed in an environmentally controlled chamberthat served as the walk-in freezer/cooler. The condenser unit wasinstalled in another chamber to control temperature. Instrumentation wasadded to the system to measure refrigerant mass flow rate, refrigerantpressure & temperature before and after each component, air temperatureand flow in/out of evaporator and condenser, and power to condensingunit and evaporator. Tests were run at two typical freezer temperatures(0° F. and −15° F.), two typical walk-in cooler temperatures (35° F. and50° F.) and a range of ambient temperatures from 55° F. to 95° F. Itshould be noted that the refrigerant temperatures were typically 15 to20° F. lower than the chamber temperatures.

The tested compositions were as follows.

TABLE 3 Commercial Name Refrigerants Tested % by weight or DesignationR-32 R-125 R-134a LT 30 30 40 LT1 25 35 40 LT2 35 25 40 R-407A 20 40 40R-407C 23 25 52R-404a is composed of 44 wt % HFC-125, 52 wt % HFC-143A and 4 wt %HFC-134a. It is a common low temperature refrigerant.

The results of the series of tests are shown in Tables 4 through 7.Table 4 lists the superheat at the exit of the evaporator. In order forthe system to operate reliably and efficiently, superheat should be inthe 8 to 16° F. (4.4 to 8.9° C.) range for moderate temperatures (e.g.35° F. and 50° F. Cooler Temp.), 8 to 12° F. (4.4 to 6.7° C.) range formoderately low temperatures (e.g. 0° F. Freezer Temp.) and 4 to 8° F.(2.2 to 4.4° C.) range for very low temperatures (e.g. −15° F. FreezerTemp.) (Ref: Sporlan Valve Company, Expansion Valve Bulletin). If thesuperheat is too low or negative, the refrigerant is in the two-phaseregion (liquid and vapor) and liquid refrigerant can be leaving theevaporator and potentially cause damage to the compressor. If thesuperheat is too high, the capacity and efficiency of the system suffersand could also cause reliability problems due to high compressordischarge temperatures.

TABLE 4 Evaporator Superheat (° F.) Refrigerant Chamber Approx. Evap.Outdoor R-407A R-407C R-404A Temp. Temp. Temp. R-22 LT LT1 LT2 No Adj.Adj TXV No Adj. Adj TXV No Adj. Adj TXV −15° F.   −30° F. 55° F. 6.787.39 6.99 5.06 2.18 — −0.51 — 19.43 — 75° F. 6.80 4.42 6.32 5.63 0.20 —−1.53 — 17.30 — 95° F. 4.94 2.92 1.90 5.06 −0.50 4.90 −1.25 — 15.48 — 0° F. −20° F. 55° F. 11.44 11.57 11.56 10.49 7.76 — 5.88 25.04 — 75° F.11.99 11.05 9.70 11.22 8.67 — 4.84 10.50 24.32 — 95° F. 9.95 8.97 9.1411.48 7.48 10.00 4.15 8.50 21.52 12.50 35° F.   15° F. 55° F. 11.6613.78 12.21 14.55 11.39 — 6.88 — 23.36 — 80° F. 10.78 11.54 10.93 12.5910.12 — 6.52 — 21.48 — 95° F. 9.08 10.39 10.01 11.78 9.11 — 5.5S — 19.789.77 50° F.   30° F. 55° F. 12.06 16.85 15.08 16.58 14.93 — 9.53 — 27.11— 80° F. 12.13 13.09 13.11 14.89 12.16 — 8.65 — 23.86 — 95° F. 10.4311.86 12.00 13.52 10.69 — 7.41 — 21.89 —From the results, it is clear that for refrigerants R-407A, R-407C, andR-404A, the expansion valve needs to be either adjusted or changed.R-407A and R-407C allows liquid to leave the evaporator at lowtemperature (noted by negative superheat numbers). R-404A has too high asuperheat, which leads to poor cooling performance.

The refrigerant mass flow, cooling capacity, and efficiency (COP) areshown relative to R-22 in the following three tables. LT, LT1, and LT2consistently show performance comparable to that of the refrigerant thesystem was designed to operate with, R-22. This is especially true forthe LT blend at the highest ambient temperature for both 0° F. and −15°F. freezer temperatures, where the match with the mass flow and capacitywith R-22 is most critical (design point of the system). LT1 and LT2also show acceptable performance considering that no adjustment orchange of the expansion valve is needed.

TABLE 5 Refrigerant Mass Flow Relative to R-22 Refrigerant ChamberApprox. Evap. Outdoor R-407A R-407C R-404A Temperature Temp. TemperatureLT LT1 LT2 No Adj. Adj TXV No Adj. Adj TXV No Adj. Adj TXV −15° F.  −30° F. 55° F. 99% 98% 97% 111% — 98% — 122% — 75° F. 101%  98% 97% 110%— 101%  — 121% — 95° F. 101%  96% 100%  115% 90% 97% — 124% —  0° F.−20° F. 55° F. 95% 100%  94% 103% — 95% 112% — 75° F. 100%  102%  88%105% — 94% 86% 115% — 95° F. 101%  103%  93% 108% 92% 97% 90% 121% 145%35° F.   15° F. 55° F. 98% 100%  93% 106% — 100%  — 114% — 80° F. 98%99% 91% 104% — 98% — 113% — 95° F. 97% 97% 90% 104% — 97% — 110% 135%50° F.   30° F. 55° F. 97% 99% 89% 104% — 99% — 109% — 80° F. 99% 101% 90% 107% — 99% — 111% — 95° F. 98% 100%  90% 107% — 98% — 113% — Averageof All Conditions 99% 99% 93% 107% 91% 98% 88% 115% 140%

TABLE 6 Refrigeration Capacity Relative to R-22 Refrigerant ChamberApprox. Evap. Outdoor R-407A R-407C R-404A Temperature Temp. TemperatureLT LT1 LT2 No Adj. Adj TXV No Adj. Adj TXV No Adj. Adj TXV −15° F.  −30° F. 55° F. 99% 90% 97% 95% — 91% — 88% — 75° F. 103%  94% 104%  98%— 99% — 87% — 95° F. 99% 89% 104%  99% 80% 93% — 83% —  0° F. −20° F.55° F. 99% 96% 100%  92% — 94% 82% — 75° F. 101%  96% 93% 94% — 91% 85%83% — 95° F. 99% 95% 97% 93% 80% 92% 88% 81% 91% 35° F.   15° F. 55° F.104%  99% 103%  100%  — 101%  — 90% — 80° F. 99% 95% 97% 95% — 97% — 84%— 95° F. 97% 92% 95% 93% — 94% — 78% 92% 50° F.   30° F. 55° F. 104% 100%  100%  100%  — 100%  — 89% — 80° F. 99% 97% 96% 97% — 97% — 83% —95° F. 98% 96% 95% 96% — 97% — 81% — Average of All Conditions 100%  96%97% 96% 80% 96% 87% 84% 92%

TABLE 7 COP (Efficiency) Relative to R-22 Refrigerant Chamber Approx.Evap. Outdoor R-407A R-407C R-404A Temperature Temp. Temperature LT LT1LT2 No Adj. Adj TXV No Adj. Adj TXV No Adj. Adj TXV −15° F.   −30° F.55° F. 99% 94% 94% 95% — 95% — 90% — 75° F. 101%  97% 101%  99% — 102% — 86% — 95° F. 98% 94% 101%  99% 89% 100%  — 84% —  0° F. −20° F. 55° F.100%  98% 98% 92% — 99% 83% — 75° F. 100%  95% 92% 94% — 95% 92% 83% —95° F. 94% 95% 93% 93% 85% 96% 93% 80% 83% 35° F.   15° F. 55° F. 106% 103%  105%  104%  — 105%  — 94% — 80° F. 98% 98% 96% 98% — 101%  — 87% —95° F. 92% 91% 91% 92% — 95% — 78% 87% 50° F.   30° F. 55° F. 105% 102%  102%  103%  — 103%  — 91% — 80° F. 95% 94% 91% 95% — 98% — 81% —95° F. 93% 93% 90% 93% — 96% — 80% — Average of All Conditions 98% 96%96% 97% 87% 99% 92% 85% 85%

TABLE 8 Expansion Valve Adjustments Impact on Performance MassRefrigerant Condition Superheat Flow Capacity COP R-404A O° F./95° F.12.5 354.6 14846 0.96 145%  91% 83% R-404A 35° F./95° F.  9.8 253.212198 1.38 135%  92% 87% R-407C O° F./95° F. 8.5 221.4 14215 1.08 90%88% 93% R-407C O° F./75° F. 10.5 213.8 15087 1.22 86% 85% 92% R-407A−15° F./95° F.    4.9 153.0  9047 0.82 90% 80% 89% R-407A  0° F./95° F.10.0 225.0 13000 0.99 92% 80% 85% Condition means chamber/outdoortemperature

R-407A and R-407C's performance at first glance looks acceptable but theR-22 expansion valve fails to operate satisfactorily over the operatingrange thereby not providing the required superheat (rise in temperature)without modification of the refrigeration system. This necessitates, ata minimum, an adjustment of this expansion valve component to increasethe superheat. The “Adj TXV” columns and Table 8 shows the performanceimpact of such an adjustment. Capacity and COP are affected resulting insignificantly lower performance than R-22 and the LT blends. R-407C'scapacity drops to only 88% of R-22's at the critical design point.Likewise R-407A has significantly lower capacity. R-404A's originalperformance showed too great a superheat so the expansion valve wasadjusted to lower the superheat. The performance improved but stillremained considerably below that of R-22 and the LT blends. It should benoted that the adjusted TXV data for R-407A at 0° F./95° F. wasextrapolated from actual test data at lower superheats (5.2 to 6.6° F.).

FIG. 1 shows the range of the components of the ternary compositions ofthis invention in the diamond shaped area in the graph and illustratesreasons why this range has considerable advantages over compositionsoutside this range designated by the dots for R-407A and R-407C. Movingup the graph from the diamond shaped area of the invention results intoo great an R-32 concentration and can result in high pressures, highsuperheat, and flammability issues. Moving down and to the left of thediamond shaped area of the invention in the graph results in lowpressures, low capacity, and lack of superheat heat using expansionvalves designed for R-22. Moving to the right of the diamond shaped areaof the invention in the graph results in higher mass flows and higherpressure and the necessity to replace the expansion valve with a new onedesigned for these conditions. The graph also illustrates the nearbyprior art compositions (R-407 A and R-407C) that do not produce therequired nearly identical match with the operating characteristics ofR-22 that the compositions of this invention produce.

While the invention has been described herein with reference to thespecific embodiments thereof, it will be appreciated that changes,modification and variations can be made without departing from thespirit and scope of the inventive concept disclosed herein. Accordingly,it is intended to embrace all such changes, modification and variationsthat fall with the spirit and scope of the appended claims.

1. A process for producing low temperature refrigeration in a lowtemperature refrigeration system suitable for use withchlorodifluoromethane (R-22) refrigerant that achieves and maintains anevaporator temperature of below 32° F. (0° C.), the process comprisingcondensing a refrigerant and thereafter evaporating the refrigerant inthe vicinity of a body to be cooled, wherein the refrigerant compositioncomprises from about 25 to about 35 mass % difluoromethane (R-32), fromabout 20 to about 40 mass % pentafluoroethane (R-125), and from about 35to about 45 mass % tetrafluoroethane (R-134a) whereby these threecomponents are present in the refrigerant composition such that theoperating characteristic of positive superheat provided duringrefrigeration is in the range of from about 80 to about 16° F. (about4.4 to about 8.9° C.) for an evaporation temperature range of about 15to 30° F. (about −9 to −1° C.), in the range of from about 8° to about12° F. (about 4.4° to about 6.7° C.) for an evaporation temperature ofabout −15° F. (about −26° C.), and in the range of from about 4° toabout 8° F. (about 2.2° to about 4.4° C.) for an evaporation temperatureof about −30° F. (about −34° C.), and the operating characteristics ofthe refrigerant composition in regard to cooling capacity, efficiency(COP), and mass flow, when employed as the refrigerant in therefrigeration system, are each at least about 95% of those operatingcharacteristics if chlorodifluoromethane (R-22) were to be employed asthe refrigerant in said refrigeration system at identical refrigerationconditions.
 2. A process for producing low temperature refrigeration ina low temperature refrigeration system suitable for use withchlorodifluoromethane (R-22) refrigerant according to claim 1 whereinthe refrigeration achieves and maintains an evaporator temperature ofabout 14° F. (−10° C.) or below.
 3. A process for producing lowtemperature refrigeration in a low temperature refrigeration systemsuitable for use with chlorodifluoromethane (R-22) refrigerant accordingto claim 1 wherein the refrigeration achieves and maintains anevaporator temperature of about 5° F. (−15° C.) or below.
 4. A processfor producing low temperature refrigeration in a low temperaturerefrigeration system suitable for use with chlorodifluoromethane (R-22)refrigerant according to claim 1 wherein the refrigeration achieves andmaintains an evaporator temperature of about −22° F. (−30° C.) or below.5. A process for producing low temperature refrigeration in a lowtemperature refrigeration system that achieves and maintains anevaporator temperature of below 32° F. (0° C.) and haschlorodifluoromethane (R-22) as a refrigerant therein, the processcomprising replacing the chlorodifluoromethane (R-22) refrigerant in therefrigeration system with a replacement refrigerant compositioncomprising the three components: difluoromethane (R-32),pentafluoroethane (R-125), and tetrafluoroethane (R-134a), condensingthe replacement refrigerant composition and thereafter evaporating thereplacement refrigerant composition in the vicinity of a body to becooled, wherein the refrigerant composition comprises from about 25 toabout 35 mass % difluoromethane (R-32), from about 20 to about 40 mass %pentafluoroethane (R-125), and from about 35 to about 45 mass %tetrafluoroethane (R-134a) whereby these three components are present inthe refrigerant composition such that the operating characteristic ofpositive superheat provided during refrigeration is in the range of fromabout 8° to about 16° F. (about 4.4 to about 8.9° C.) for an evaporationtemperature range of about 15 to 30° F. (about −9 to −1° C.), in therange of from about 8° to about 12° F. (about 4.4° to about 6.7° C.) foran evaporation temperature of about −15° F. (about −26° C.), and in therange of from about 4° to about 8° F. (about 2.2° to about 4.4° C.) foran evaporation temperature of about −30° F. (about −34° C.), and theoperating characteristics of the refrigerant composition in regard tocooling capacity, efficiency (COP), and mass flow, when employed as therefrigerant in the refrigeration system, are each at least about 95% ofthose operating characteristics if chlorodifluoromethane (R-22) were tobe employed as the refrigerant in said refrigeration system at identicalrefrigeration conditions.
 6. A process for producing low temperaturerefrigeration in a low temperature refrigeration system according toclaim 5 wherein the refrigeration achieves and maintains an evaporatortemperature of about 14° F. (−10° C.) or below.
 7. A process forproducing low temperature refrigeration in a low temperaturerefrigeration system according to claim 5 wherein the refrigerationachieves and maintains an evaporator temperature of about 5° F. (−15°C.) or below.
 8. A process for producing low temperature refrigerationin a low temperature refrigeration system according to claim 1 whereinthe refrigeration achieves and maintains an evaporator temperature ofabout −22° F. (−30° C.) or below.
 9. A process for producing lowtemperature refrigeration in a low temperature refrigeration systemaccording to claim 5, the process comprising essentially totallyreplacing the chlorodifluoromethane (R-22) refrigerant in therefrigeration system with the replacement refrigerant composition.
 10. Aprocess for producing low temperature refrigeration in a low temperaturerefrigeration system according to claim 6, the process comprisingessentially totally replacing the chlorodifluoromethane (R-22)refrigerant in the refrigeration system with the replacement refrigerantcomposition.
 11. A process for producing low temperature refrigerationin a low temperature refrigeration system according to claim 7, theprocess comprising essentially totally replacing thechlorodifluoromethane (R-22) refrigerant in the refrigeration systemwith the replacement refrigerant composition.
 12. A process forproducing low temperature refrigeration in a low temperaturerefrigeration system according to claim 8, the process comprisingessentially totally replacing the chlorodifluoromethane (R-22)refrigerant in the refrigeration system with the replacement refrigerantcomposition.
 13. A process for producing low temperature refrigerationaccording to claim 1 wherein the refrigeration system is a new lowtemperature refrigeration system suitable for use withchlorodifluoromethane (R-22) refrigerant.
 14. A process for producinglow temperature refrigeration according to claim 2 wherein therefrigeration system is a new low temperature refrigeration systemsuitable for use with chlorodifluoromethane (R-22) refrigerant.
 15. Aprocess for producing low temperature refrigeration according to claim 3wherein the refrigeration system is a new low temperature refrigerationsystem suitable for use with chlorodifluoromethane (R-22) refrigerant.16. A process for producing low temperature refrigeration according toclaim 4 wherein the refrigeration system is a new low temperaturerefrigeration system suitable for use with chlorodifluoromethane (R-22)refrigerant.
 17. A process for producing low temperature refrigerationin a low temperature refrigeration system according to claim 1 whereinthe process requires no adjustment or replacement of any expansion valveof the low temperature refrigeration system to obtain the said operatingresults.
 18. A process for producing low temperature refrigeration in alow temperature refrigeration system according to claim 5 wherein theprocess requires no adjustment or replacement of any expansion valve ofthe low temperature refrigeration system to obtain the said operatingresults.
 19. A process for producing low temperature refrigeration in alow temperature refrigeration system according to claim 9 wherein theprocess requires no adjustment or replacement of any expansion valve ofthe low temperature refrigeration system to obtain the said operatingresults.
 20. A process for producing low temperature refrigeration in alow temperature refrigeration system according to claim 13 wherein theprocess requires no adjustment or replacement of any expansion valve ofthe low temperature refrigeration system to obtain the said operatingresults.
 21. A process for producing low temperature refrigeration in alow temperature refrigeration system according to claim 1, wherein therefrigerant composition comprises about 30 mass % difluoromethane(R-32), about 30 mass % pentafluoroethane (R-125), and about 40 mass %tetrafluoroethane (R-134a).
 22. A process for producing low temperaturerefrigeration in a low temperature refrigeration system according toclaim 5, wherein the refrigerant composition comprises about 30 mass %difluoromethane (R-32), about 30 mass % pentafluoroethane (R-125), andabout 40 mass % tetrafluoroethane (R-134a).
 23. A process for producinglow temperature refrigeration in a low temperature refrigeration systemaccording to claim 9, wherein the refrigerant composition comprisesabout 30 mass % difluoromethane (R-32), about 30 mass %pentafluoroethane (R-125), and about 40 mass % tetrafluoroethane(R-134a).
 24. A process for producing low temperature refrigeration in alow temperature refrigeration system according to claim 13, wherein therefrigerant composition comprises about 30 mass % difluoromethane(R-32), about 30 mass % pentafluoroethane (R-125), and about 40 mass %tetrafluoroethane (R-134a).
 25. A process for producing low temperaturerefrigeration in a low temperature refrigeration system according toclaim 17, wherein the refrigerant composition comprises about 30 mass %difluoromethane (R-32), about 30 mass % pentafluoroethane (R-125), andabout 40 mass % tetrafluoroethane (R-134a).
 26. A process for producinglow temperature refrigeration in a low temperature refrigeration systemaccording to claim 18, wherein the refrigerant composition comprisesabout 30 mass % difluoromethane (R-32), about 30 mass %pentafluoroethane (R-125), and about 40 mass % tetrafluoroethane(R-134a).
 27. A process for producing low temperature refrigeration in alow temperature refrigeration system according to claim 19, wherein therefrigerant composition comprises about 30 mass % difluoromethane(R-32), about 30 mass % pentafluoroethane (R-125), and about 40 mass %tetrafluoroethane (R-134a).
 28. A process for producing low temperaturerefrigeration in a low temperature refrigeration system according toclaim 20, wherein the refrigerant composition comprises about 30 mass %difluoromethane (R-32), about 30 mass % pentafluoroethane (R-125), andabout 40 mass % tetrafluoroethane (R-134a).
 29. A low temperaturerefrigeration system suitable for use with chlorodifluoromethane (R-22)refrigerant, the low temperature refrigeration system being capable ofproducing low temperature refrigeration achieving and maintaining anevaporator temperature of below 32° F. (0° C.), the system comprising acondenser, an evaporator and a refrigerant composition, wherein therefrigerant composition comprises from about 25 to about 35 mass %difluoromethane (R-32), from about 20 to about 40 mass %pentafluoroethane (R-125), and from about 35 to about 45 mass %tetrafluoroethane (R-134a) whereby these three components are present inthe refrigerant composition such that the operating characteristic ofpositive superheat provided during refrigeration would be in the rangeof from about 80 to about 16° F. (about 4.4 to about 8.9° C.) for anevaporation temperature range of about 15 to 30° F. (about −9 to −1°C.), in the range of from about 8° to about 12° F. (about 4.4° to about6.7° C.) for an evaporation temperature of about −15° F. (about −26°C.), and in the range of from about 4° to about 8° F. (about 2.2° toabout 4.4° C.) for an evaporation temperature of about −30° F. (about−34° C.), and the operating characteristics of the refrigerantcomposition in regard to cooling capacity, efficiency (COP), and massflow, when employed as the refrigerant in the refrigeration system,would each be at least about 95% of those operating characteristics ifchlorodifluoromethane (R-22) were to be employed as the refrigerant insaid refrigeration system at identical refrigeration conditions.
 30. Alow temperature refrigeration system suitable for use withchlorodifluoromethane (R-22) refrigerant according to claim 29 and beinga low temperature refrigeration system that previously employedchlorodifluoromethane (R-22) refrigerant as the refrigerant therein. 31.A low temperature refrigeration system suitable for use withchlorodifluoromethane (R-22) refrigerant according to claim 29comprising a new low temperature refrigeration system suitable for usewith chlorodifluoromethane (R-22) refrigerant.